This topic was covered in some depth by Iain M. Banks in his novel Surface Detail and reanimated in The Hydrogen Sonata (which I haven't finished yet, so don't tell me!). The stuff in Surface Detail is amazing and over the top. This is from The Hydrogen Sonata:

Some civ[ilization]s, admittedly, simply weren’t having any of this, and routinely bred whole worlds, even whole galaxies, full of living beings which they blithely consigned to oblivion the instant they were done with them, sometimes, it seemed, just for the glorious fun of it, and to annoy their more ethically angst-tangled co-civilisationalists, but they – or at least those who admitted to the practice, rather than doing it but keeping quiet about it – were in a tiny minority, as well as being not entirely welcome at all the highest tables of the galactic community, which was usually precisely where the most ambitious and ruthless species/civs most desired to be.Others reckoned that as long as the termination was instant, with no warning and therefore no chance that those about to be switched off could suffer, then it didn’t really matter. The wretches hadn’t existed, they’d been brought into existence for a specific, contributory purpose, and now they were nothing again; so what?

This moment, right now is the moment you have been brought into existence. In just a moment, you will realize that all the events that you think brought you to this point are implanted memories, and you are an artificial brain trapped in a malicious creators device. Clench up your butt cheeks. This next part is going to be a doozy.